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        <title>Pairing parameters</title>
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            Pairing parameters
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        Pairing parameters refer to a subset of pairing criteria as described in <a href="Pairing evaluation function.html">Pairing evaluation function.</a>
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            <img src="images/pairingparameters_001.jpg">
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        <h2>Main criteria</h2>
        A "group" is a set of players with same score for main placement criterion (MMS or NBW).
        <h3>Avoid mixing categories</h3>
        Relevant in "Swiss with categories" only. When selected, the pairing will prefer intra-category pairing.
        <h3>Minimize score differnece</h3>
        Always selected. Pairing prefers to pair players with equal or neighboring main score, MMS or NBW.
        <h3>Seeding system</h3>
        Inside a group, players are ordered according to of their placement. Each player of the higher half of the group will be paired with a player of the lower half.
        <br>"Split and Fold" will prefer pairs on the "1 - n, 2 - n-1, ..." scheme
        <br>"Split and Slip" will prefer pairs on the "1 - n/2+1, 2 - n/2+2, ..." scheme
        <br>"Split and Random" will make random choice.
        <br>You can choose a different system for former rounds and latter rounds.
        <br>And, for former rounds, you can add a sorting on rating. This is the recommended mode if you want to avoid a game between two best players in the former rounds.
        <h3>When pairing players from different groups ...</h3>
        Difficulties or impossibility to make intra-group pairing (due to uneven size of a group, for instance) may occur.
        <br>When this occurs, OpenGotha will choose one player in the group and this player will be paired with a player of a stronger or weaker group.
        <br>OpenGotha will try to do not draw-up or draw-down a player twice in the same direction. It will also try to compensate a previous draw-up by a drow-down and vice versa.
        <br>It will also prefer to chose drawn-up and drawn-down players according to your choice, in the top, middle or bottom of the group.

        <h2>Base criteria</h2>
        <h3>Avoid pairing same pair twice</h3>
        Always selected
        <h3>Random</h3>
        OpenGotha can introduce a part of random in pairing. If you choose to accept random, you will have to choose between :
        <ul>
            <li> Deterministic random. Two successive pairings will give exactly the same pairing</li>
            <li> Non-Deterministic random. Two successive pairings may give different pairings</li>
        </ul>
         <h3>Balance White and Black</h3>
         Always selected. Tends to give the same number of games with white and black for a given player.

        <h2>Secondary criteria</h2>
        Secondary criteria are  "Minimize handicap" criterion and geographical criteria.
        Secondary criteria are, by default, applied.
        But you can exclude these criteria for some defined players :
        <ul>
            <li>Players above a certain rank</li>
            <li>Players with a good performance in previous games.
                <br>For instance, in a 10 rounds tournament, if you select this option, then players having at least 5 wins in their previous games will not be concerned by these secondary criteria.
            </li>
        </ul>
        <h3>Minimize handicap</h3>
        This criterion is already taken in account in Mac-Mahon system because intra-group pairing will not lead to handicaps.
        <br> It may be more relevant in swiss system when handicap is permitted.
        <br>Details in <a href="Pairing evaluation function.html">Pairing evaluation function.</a>
        <h3>Avoid intra-country pairing and Avoid intra-club pairing</h3>
        This determines what you accept to do to avoid intra pairing.
        <br>For instance, in a Mac-Mahon tournament,
        if you choose 3 as group gap, which is the default value for intra-club pairing,
        then OpenGotha will prefer to pair a given player with an other player coming from an other club even if their
        MMS difference is up to 3 points rather than to pair him with a player coming from the same club with same MMS value.

        
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